Electronic musical instrument

ABSTRACT

A wind-actuated electronic musical instrument for play by a musican. The musician uses substantially the same technique as is associated with acoustic wind instruments to vary the range of musical sound and expression produced by the electronic musical instrument. Transducers convert the musician-produced air flow, lip pressure and fingering of the instrument to appropriate electrical signals, which signals control the frequency, harmonic content and harmonic phase of the sound produced by a tone generator.

United States Patent 1191 1111 3,767,833 Noble et al. 1 Oct. 23, 1973 [54] ELECTRONIC MUSICAL INSTRUMENT 3,307,050 2/1967 Castle 84/].11 x 3,429,976 2/1969 Tomcik.... 84/112 [751 lnvemms' 3,439,106 4 1969 GOOdaie 84/].27 Bernard, both of NOW/e", Mass- 3,493,669 2 1970 Elbrecht et a1. 84 1.11 x [73] Assignee: Computone, lnc., Hanover, Mass. OTHER PUBLICATIONS [22] Filed: Oct. 5, 1971 Robert Moog, The Theremin", Radio & Television News, Feb. 1954, pp. 37-39 [21] Appl 186645 Robert Moog, A Transistorized Theremin, Electronics World, Jan. 1961, pp. 29-31 [52] US. Cl 84/l.0l, 84/l.l l, 84/l.l9,

34/122 84/124 Primary ExaminerRichard B. Wilkinson [51] Int. Cl. Gl0h 1/04, GlOh 3/00 4s s i {q t Examiner-Stanley .l. Witkowski [58] Field of Search 84/1.0l, 1.04-1.12, Attorney-John A. Lahivedr. 84/1.l91.24, 1.27

[57] ABSTRACT [56] Re ren s C t d A wind-actuated electronic musical instrument for UNITED STATES PATENTS play by a musican. The musician uses substantially the 3,255,296 6/1966 Peterson 84/l.24 same technique as is amciated with amustic Wind 3,316,341 4 1967 Peterson 84/].24 strumems to vary the range of musical Sound and 3,655,904 4/1972 C h 34/191 pression produced by the electronic musical instru- 1,661,058 2/1928 Theremin.. 84/123 ment. Transducers convert the musician-produced air 2,133,500 11/1933 84/11 X flow, lip pressure and fingering of the instrument to 2,301,134 11942 f" 84/1-01 appropriate electrical signals, which signals control agf Q 2 the frequency, harmonic content and harmonic phase 1e 3,098,407 7/1963 Brand et al.-

84/Hl of the sound produced by a tone generator. 3,231,660 I/l966 Munch 84/l.1l 24 Claims, 14 Drawing Figures KEYING OSCILLATOR A ADDER (ekwegi LAG uekmegi FREQUENCY e9 (ADJ) \lol CONTROL T 100 A e as 7 /1 1 ea: MAIN SIGNAL OUTPUT g ADDER COMPARATOR fi M To FILTERS e D.C.REFERENCE Qt ie k4 i09 g+(e +Dg) (Ill J BAND PASS ADDER LAG FILTERS OVERTONE SELECTOR CIRCUIT "4 no r 112, i l ANALOG l 2 -11 ADDER FUNCTION S'E TE SJE FlTTER 1 i 1 1 U xe +1 e H6 1 F:

: 117 ADDER ADDER 1 1 OVERTONE SELECTOR 11 1 ABSOLUTE VALUE C lRCUIT k 9 FROM OUTPUT OF 1 g 1 9 12a PATENTED 0H 2 3 i975 SHEET 5 BF 9 .rDnEbO wuzmmwmmm 0 0 .l. 12 WEEK 29528 515532 f m; Eta zoEzE 531532 6E T n: Eta 29522 $31532 Q 6: 5t; 29525 $15532 5 E Q91 5:; 3V1}; 2952B 0 515532 1 or.

1 ELECTRONIC MUSICAL INSTRUMENT FIELD OF THE INVENTION This invention relates in general to electronic musical instruments and more particularly to an electronic musical instrument capable of translating into sound the various and complex shadings of expression and embellishments manifest in the talent and ability of a performer.

BACKGROUND OF THE INVENTION Acoustical wind instruments are, of course, long known in the musical art and include a variety of reed- /air column instruments exhibiting highly complex acoustical properties and having the capability of being played with a wide range of expression. A musician obtains his expression and tonal quality with these instruments by a combination of lip configuration and pressure, commonly referred to as embouchure, by controlling the air flow he supplies to the instrument to provide a certain characteristic attack to a performance and also by keying to vary the pitch or frequency of the tones being produced. In playing a reed instrument, the source of the acoustic tone may be considered to be the vibrating reed with the characteristic sound produced by the performance being a combination of -the modifying effects of the acoustic resonance formed by the horn coupled to the reed and also of the anatomy of the performer coupled to the reed. The control exerted by the performer through embouchure and breath control, as well as the fingering of the keys is highly variable, very flexible, and can therefore be higher expressive.

The general tonal quality or timbre of the instrument results from the combination of the fundamental tone selected from the reed by the horn with contributions from the harmonics of this fundamental. The contribution to the entire tone from each of the harmonics results from the acoustic filtering action of the instrument. While the particular choice of instrument results in a particular tonal structure for a given lip pressure, breath flow and note, this tonal structure is highly variable for a given note by varying lip pressure and breath flow.

Thus the same note on the same instrument played by different performers or even by the same performer in a different manner may have different tonal structure. It is key to an understanding of the musicians performance on a wind instrument to realize that as the ear of the performer hears the sounds being emitted, his brain controls his lip pressure and breath to modify the sound as it is being played. In modern technological parlance, there is a closed feedback loop including the acoustic output from the horn and performer, which is sensed by the ear, relayed to the brain, which in turn provides control signals to the muscles which affect the lip pressure and breath supply to themselves modify and control the sound output. The wind instruments have a very large degree of expression in performance that horn and the coupling of the acoustic system of the performer to this horn. Thus, two different people having different anatomies may be almost incapable of producing the same sounds from the same instrument, even given the same level of expertise. Similarly the sophistication of embouchure required to play the instruments consistently to produce the same sounds at will, requires a great deal of training. Again, the physical ability needed to produce the air flow for the instruments and the muscular strength to play the instrument, may vary in the same individual from time to time and under a variety of conditions. Thus the player commencing a long performance may be capable of producing notes from the horn, which he is physically incapable of producing at the beginning or at the end of that same performance. Also performers, having once attained a level of skill, may, as they grow older, lose the physical abilities necessary to produce the same musical performance. Another limitation of some acoustic woodwind instruments resides in the complexities of fingering, since the placement of the keys is necessarily limited because of the length of the air columns being controlled and accordingly some transitions from one fingering position to another may be awkward or even substantially impossible, thus limiting the musical transitions that may be accomplished with that instrument. Again the fingering required to produce a certain note in one octave of an instrument being played over a three octave band, may of necessity differ from the fingering required to produce the same note in a different octave. In addition, some instruments do not intonate properly until after a warm-up period.

One recent development in musical instruments has been the application of electronic oscillators to generate electrical signals driving electroacoustic loud speakers to produce musical sounds. A relatively common implementation of this concept is the electronic organ. Others include electronic synthesizers and various electronic auxiliary boosters to amplify, or modify at least portions of the sound being produced by conventional acoustic musical instruments. None of these electronic musical instruments, however, are closely coupled to the performer and consequently they are not capable of being played with a wide range of expression. Thus the electronic organ may be played to produce, for each key, a pure tone. However, the performers expression is limited to a basically digital form, since the key plays precisely the same note no matter how it is struck. In these electronic organs, it is possible to add a vibrato by means of an auxiliary key which produces a precise and mechanical ringing of the note which is struck by pulsating according to a predetermined variation. This vibrato differs a great deal from the vibrato produced by a performer on a wind instrument in which he produces a pulsation of frequency and amplitude which he can individually control. v I

There have been some attempts to substitute for the acoustic tone generator in a wind instrument, an electronic signal generator and electroacoustic loud speaker combination. One such instrument is described in US. Pat. No. 2,301,184. In that patent, the frequency of the output sounds is controlled by keying, which is controlled by electronic switches in the same fashion as the electronic organ, while the amplitude of the output sound is modified by means of a rheostat response to lip pressure. Employing such a device, the

the amplitude of that same note. A switch enabling the electronic tone generator to produce signals is operated by the performers breath, so that it is necessary for him to blow into the instrument at a certain rate, in order to actuate the switch. This breath transducer is, however, simply an on-off switch for the electronic tone generator.

A somewhat more sophisticated approach is described in U.S. Pat. No; 3,439,106. In that patent an instrument is described which includes an air flow transducer producing output electrical signals varying in proportion to air flow through the mouthpiece of the instrument. This air flow signal is used to control and vary the amplitude of the output tones produced by an electronic signal generator. The frequency or pitch of the tones produced is controlled by fingering the keys. Again this instrument is limited in its performance characteristics, since it includes, in addition to the keying, only one variable control, namely the breathamplitude effect. Such instruments are extremely limited terms of musical expression and might be more difficult to play well than the corresponding acoustic instrument.

BRIEF SUMMARY OF THE INVENTION Broadly speaking, the electronic musical instrument of this invention comprises an electronic tone generator, which is controlled by a combination of transducer signals (DC. control voltages) produced by an air flow transducer at the mouthpiece of the instrument by a lip pressure transducer at the mouthpiece of the instrument and by the fingering or key signals. Thus the instrument may be played with much the same physical control variables that are present in playing the acoustic wind instruments. However, the same acoustic range may be produced within a range of air flow which is adjustable in quantity from less than that required to play a woodwind instrument to any comfortable value. Similarly the modifying effect of any one of the factors may be employed with any weighting factor and time delay to vary the amplitude, the pitch, the timbre and the time duration of the resulting tones. The tone generator of the instrument, is a voltage controllable (voltage to frequency) electronic oscillator producing a triangular waveform in a frequency range set prior to the performance with the specific frequencies of individual notes (voltages) being selected by the fingering on the instrument.

This output waveform is applied to a comparator and compared with a manually adjustable DC voltage to which may be added weighted outputs from the lip and- /or wind transducer, thereby varying the effective duty cycle of the comparator output. The output square wave from the comparator is then fed to a signal lag circuit, producing a generally sawtooth waveform in which the ratio of rise to fall time and hence the harmonic components vary with the DC comparison voltage. Thus the comparator and lag circuit affect the frequency spectrum of this signal. This signal may be supplied to an amplitude modulator which is principally controlled by the breath transducer. The resultant modulated voltage output signal may be employed directly to drive an amplifier and an audio output device such as an acoustic loudspeaker, or earphones. The signal may also be recorded on a storage medium, such as magnetic tape for later conversion to audio signals. Alternatively, and more effectively in the preferred embodiment of this invention, the comparator output is supplied to a parallel array of bandpass filters. These filters are voltage controllable so that their center frequency varies in proportion to' the voltage applied to their control inputs. With the control inputs connected to the output of the keying circuit, the center'frequencies of the filters will track to match the change in frequency of the main tone generator. The difference in frequency between each of the filters (as compared to the main tone generator) may be adjusted to conform to a desired series such as the natural series (f, 2f, 3f, 4f, 5f, nj), where f represents the frequency of the main tone generator.

The tuning is accomplished by the same keying voltage that tunes the main tone generator.

In the acoustic instruments, the horn section may be analyzed as an active filter, tunable by keys or slides which reinforces the fundamental and certain overtones depending on the design of the instrument, the design of the mouthpiece and the players embouchure. The live sound of acoustic instruments derives from the ability of the player to change, at will, the harmonic content of the output as well as the phase relation of the harmonics with respect to each other and the fundamental.

By applying the output of the lip transducer to the filter center frequency control inputs, in addition to the main tuning voltage, it is possible to change the phase of the harmonics as in the acoustic instruments. By employing the lip transducer to change the duty cycle" of the comparator, the harmonic content of the tone input to the filters may be varied. If the lip transducer output voltage signal is added to the main tone generator frequency control voltage (keying signal), the frequency of the main tone generator may be varied to provide a glissando that is essentially the same type of gliss as is obtained in the acoustic instruments.

Provision is made for weighting and delaying these effects, as well as the proportion of the harmonics in the output independently, therefore providing an extremely wide range of Phase/frequency/harmonic content interdependence. Since the O of the filters is adjustable from a highly-damped state to an oscillatory state, it is possible to make the timbre of the instrument cover a range of tonal coloration not possible in the acoustic instruments.

It will thus be understood that, as in conventional woodwind instruments, the harmonic composition or timbre of the produced sounds may be controlled by both the air flow and the lip pressure, as well as the selected key. As described earlier, it has been found that in wind instruments, the contribution from the overtones of a particular note will vary, depending upon lip pressure, how hard the instrument is blown, and the range the instrument is being played in. The electronic instrument of this invention, allows the performer a similar degree of expression. While, in the acoustic instrument, the fingering arrangements were limited by the physical properties of the horn as an acoustic air column, the fingering position in the electronic instrument may be entirely related to the players manipulative convenience. Accordingly, unlike acoustic instruments, the same letter note may be played by the same fingering arrangement in any one of the octaves in which the instrument is being played. A fingering system has been devised which is closely related to conventional woodwind fingering techniques. A cumulative chromatic fingering logic circuit allows the convenient playing of sharps or flats or double sharps or double flats of any note on the scale. This fingering system removes many of the limitations experienced in acoustic instruments in making certain transitions from some notes to some others.

OCTAVE KEY SILENCING CIRCUIT In order that an unwanted output signal not be heard when an octave shift is made, an output silencing circuit is incorporated. A silencing signal is subtracted from the main wind signal during and in proportion to the magnitude of frequency shift due to keying. (Note: It is not physically possible to coordinate key shift and breath articulation as fast as the circuitry is able to respond). This is accomplished by differentiating the absolute value of the lagged keying signal, weighting the derivative, and subtracting it from the wind (amplitude) signal. If a large change is made, the system can be adjusted to reduce the output to zero. This simulates the acoustic instruments proportional speaking delay which arises from the instruments inability to change modes instantaneously.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration in perspective view of the mouthpiece and key sections of a musical instrument constructed in accordance with the principals of this invention;

FIG. 2 is an illustration in perspective view from the opposite side of the mouthpiece and key sections of the instrument illustrated in FIG. 1;

FIG. 3 is an enlarged cross sectional view of the mouthpiece section of the instrument of FIG. 1;

FIG. 4 is an illustration in schematic form ofa circuit for use with the air flow transducer portion of the mouthpiece illustrated in FIG. 3;

FIG. 5 is an illustration in schematic form ofa circuit useful with the Reed transducer included in the mouthpiece illustrated in FIG. 3;

FIG. 6 is an illustration in block diagrammatic form of the circuitry used in conjunction with the mouthpiece and key system illustrated in FIG. 1;

FIG. 7 is an illustration in schematic form of a filter circuit useful in the system illustrated in FIG. 6;

FIG. 7a is an illustration of a typical frequency response characteristic of the filter section of FIG. 7;

FIG. 8 is an illustration partially in block diagrammatic and partially in schematic form of a wind overtone circuit useful in the system illustrated in FIG. 6;

FIG. 9 is an illustration in graphical form of the output signal characteristic from the circuit of FIG. 8;

FIG. 10 is an illustration generally in diagrammatic form of a keying circuit useful in the instrument illustrated in FIG. 1; and

FIGS. 11, 12 and 13 are fingering charts useful in operating the musical instrument illustrated in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawings, the mouthpiece and key sections of the electronic wind instrument of this invention are shown in FIGS. 1, 2 and 3, while FIG. 6 is a general block diagram of the circuitry components of the system for the instrument. The instrument has a generally tubular body 11 including a mouthpiece section 12 with a reed 13. A set of keys 21, 24, 25, 26, 29, 30 and 31 are arranged for selecting the notes, keys 22, 23, 27 and 28 are arranged for selecting chromatics, while on the opposite side of the body a pair of octave keys 32 and 33 are located together with a thumb rest 34. A combination thumb rest and electrical connector 15 provides for taking the output signal leads from the tube to the console which contains the circuit elements illustrated in FIG. 6. The mouthpiece 12 is formed as a conventional single reed woodwind mouthpiece with the reed typically being made of cane or plastic. The instrument may, therefore, be played as a conventional wind instrument in terms of embouchure and air flow. In this instrument the performers breath is blown through a passage 18, but it does not generate sound, as do conventional wind instruments. Rather, the air flow is sensed by a pressure transducer and then passes out through an opening 17 in the mouthpiece. The opening 17 is partially blocked by an adjustable thumb screw 14 so that the pressure within the passage may be varied to provide appropriate feel for the player and to vary the sensitivity of the transducer to air flow.

The wind transducer, as is most clearly illustrated in FIG. 3 includes a flexible membrane 40 positioned along one wall of the passage 18. Directly overlying the flexible membrane 40 is a spring element 41 having an offset portion which interrupts light passing from alight source 43 to an aperture in a light tight enclosure 45 within which is located a photocell 44. The light source 43 may take any suitable form, a light emitting diode being a preferred one. operationally, an increase in air flow produces an increase in pressure within passage 18 thereby deflecting the spring element 41 intercepting a larger proportion of the light emitted by the light source 43, with a consequent decrease in illumination of the photocell 44.

In FIG. 4 there is illustrated a circuit for use with the air flow transducer illustrated. The photocell 44 is shown connected in series with the resistor 51 between a positive voltage supply +V and a negative voltage supply V. From the junction between the resistor 51 and the photocell 44 an operational amplifier 50 is connected through the series combination of a pair of light emitting diodes 43 and 52 to the positive voltage supply +V. In operation, a decrease in light from the diode 43 reaching photocell 44 results in an increase of current supplied by the operational amplifier 50 to the diodes and consequently in an increase in brightness of both light emitting diode 43 and light emitting diode 52. The diode 52 may therefore be considered as a slave" diode to diode 43 which provides a light output which varies directly with variations in pressure. The corresponding variation in light output from diode 52 may then be used as a breath flow transducer signal byincluding an appropriately positioned photocell in other response circuits. It will be understood that while this particular form of air flow transducer has been illustrated, other techniques, such as a hot wire air flow or the like may be employed.

The second transducer in the mouthpiece portion of the instrument is one which responds to lip pressure on the reed 13. This transducer includes a thin armature 47 formed of magnetic material attached to the inner surface of the reed 13. This armature is positioned with respect to a three legged inductance core 48, so that in the normal or rest position, the armature does not come in contact with the core 48. The coupling achieved between the legs of inductance core 48 and thearmature is a function of reed position and therefore of lip pressure. The core 48 is part of a reluctance bridge 49, as illustrated in FIG. 5. On each leg of the core 48 there is wound an inductance 59, 60 and 61 respectively. The inductance coil 60 is actuated by an oscillator 58 while inductance coil 59 has one terminal connected to ground and the other connected in series with diode 62 and capacitor 64 to ground. The other side of the bridge is symmetrical and includes a connection from one terminal of inductance 61 through diode 63 and capacitor 65 to ground, the second terminal of inductance 61 being connected directly to ground. The junction between diode 62 and capacitor 64 is connected through resistor 71 and 72in series to the junction between diode 63 and capacitor 65. The input to an operational amplifier 74 is connected from the midpoint between resistors 71 and 72. The output voltage, e.g., from the amplifier 74 serves as the output signal from the reed transducer. A threshold control is provided by a potentiometer 70 connected between a positive voltage +V and the input to operational amplifier 74. A feedback resistor 75 is coupled around operational amplifier 74.

The operation of the circuit is such that when the reed is at rest, the armature is displaced asymmetrically from all three core inductances and the reluctance bridge is unbalanced. When the reed is squeezed by the lips into the normal playing position, the inductance 60 is coupled through the armature 47 to the inductance 61 with a higher coupling factor then it is to inductance 59. Under these conditions the bridge is unbalanced. As the reed is squeezed more tightly by the lips, the coupling becomes equalized and the bridge becomes more balanced. Initially the threshold potentiometer 70 is adjusted so that for a particular condition of imbalance of the bridge, there is no output signal from the operational amplifier 74. As the reed is squeezed and the armature position produces equal coupling between the inductances, the operational amplifier then provides an output signal proportional to reed position. As in the case of the air flow transducer, the invention is not limited to the particular reed transducer illustrated.

The keying elements of the instrument provide for an output voltage, which varies in direct response to the keys which are closed, thereby providing the control voltage, e which varies with the notes being played. The keying system is generally a modified Boehm system. The precise arrangement of the keying circuit will be described in detail below in conjunction with the discussion of FIGS. through 13.

In general, then, the' electrical output from the mouthpiece and keying section consists of three signals, the air flow transducer output signal, 2 the reed transducer output signal, e,, and the output signals responsive to the key positions, e

In FIG. 6 there is a block diagram of the overall electronic circuitry of the musical instrument, which circuitry would usually be included within a console. The specific components indicated in FIG. 6 as adders, subtractors, lag circuits, absolute value circuits and function fitters are well known in the art, as exemplified for instance in the Handbook of Operational Amplifier Applications, Burr-Brown, Tucson, Ariz., 1963, pp. 57, 59, 67 and 69 and Applications Manual For Operational Amplifiers published by Philbrick/Nexus Research, A Teledyne Company, Dedham, Mass, 1968 at Sections 11.15, 11.16, 11.3, 11.4 and 11.5. The output signal, e from the air flow transducer is applied through subtractor 126 as one input to a modulator 121, the output of which is coupled through adder 123 and amplifier 124 to an output loud speaker 125. If the transducer is as illustratedin FIG. 3, this output signal e applied to the modulator 121 may be in the form of the light from the second light emitting diode. The main signal source for the musical instrument is supplied from an oscillator 102. This oscillator is a voltage controlled, constant amplitude, variable frequency oscillator which has its control signal supplied from adder through an adjustable keying lag circuit 101. As indicated the adder has supplied to it the keying signal 2,, and also the reed or gliss signal (2,. The keying signal will in general provide the main control to the variable frequency oscillator 102 and the reed signal, e,, may have zero contribution or a variable amount of contribution depending upon the lip pressure applied to the reed by the performer. The output signal from the adder 100 may be represented as e De, where D is.

a constant applied to the reed signal in order to weight its effect on the oscillator control. The keying lag 101 is a conventional lag circuit in which step changes in the applied signal are converted into a slow rise time signal, the amount of lag controlling the response-time characteristic of the instrument.

The output signal, e,, from the oscillator is applied as one input to an adder 104, which provides its output to comparator 106, the output from the comparator being supplied through signal lag circuit 108 to a series of bandpass filters 111. The reed signal, e,, and the air flow transducer signal, e,,,, are also supplied as inputs to adder 104. A manual timbre control 107 on adder 104 provides for varying the zero reference level on which the sawtooth waveform output from oscillator 102 is superposed. The purpose of the elements including adder 104, comparator 106' and signal lag 108 is to provide a generally sawtooth wave having a variable'ratio of rise to fall time. Since the shape of the waveform varies, the frequency components within the waveform will vary and hence the harmonic structure of the resultant signal eventually applied to the audio output. Therefore this group of circuit elements primarily controls the timbre of the instrument. The comparator 106 is a bistable circuit having a preset threshold such that when the input sawtooth applied to it is above the specific threshold level, the comparator provides one level of output signal and when it is below that threshold it provides a different output signal level. The output from the comparator 106 istherefore a variable ,duty cycle square wave, with the frequency following the oscillator frequency and the duty cycle being controlled by the manual timbre reference voltage, e,. The signal lag circuit 108 converts this variable duty cycle square wave into a generally sawtooth wave, the shape of the sawtooth wave, being controlled by the square wave duty cycle. Also applied to lag circuit 108 is a reference voltage directly from the output'of adder 100, the reference voltage therefore representing the signal e De This voltage serves to maintain a constant peak to peak amplitude output from element 108 despite variations in the input frequency.

The bandpass filters 111 consist of a series, typically five, voltage-controlled bandpass filters arranged normally in the natural series, providing bandpass charac- I ducer (e,) and also from the output of adder 100. The

outputs from adder 109 may be represented as e,, (e De,). The degree to which this control signal varies the center frequencies and the weighting factors of each of the band pass filters. about the normal by contributions from the lip transducer may be varied by initial adjustment. The output signals from the filters 1 11 are supplied to adder 120, where they are summed and the resultant output signal is applied as a second signal to modulator 121.

Thus, if the overtone selector circuit 114 is not considered, the output signal from the modulator 121 which drives the adder 123, amplifier 124, and loud speaker 125 consists of the sum of the outputs from the band pass filters 1 1 1, modulated bythe output signal e from the air flow transducer. It should be noted that the system may be operated without the band pass filters 111. In this latter circumstance the output signal from the signal lag unit 108 would be applied directly as one of the modulator signals to modulator 121 and the resultant output signalto the amplifier 124 and audio output device, shown here as loud speaker 125 would therefore consist of the variable rise and fall time sawtooth wave amplitude'mo'dulated by the signal 'e,,, from the air flow transducer. In the preferred form,"however, band passfilters 111 are interposed between the signal lag'unit 108 output and the adder 120 and thus the overtone structure'of the final resultant tone can be more directly. controlledby virtue of lip pressure.

It will be understood that while the center frequencies of each of the band pass filters are generally preset and, as noted would generally be in the same relationship as the natural series, they may be varied by preadjusted settings to any desired combination, e.g., to conform to the typical overtone spacing of a conventional wind instrument, for example, a clarinet. Similarly, while only four output signals have been shown, it will be clear that the designations F F and F indicate that any number of filters may be used. '1

A secondary circuit subsystem for use with the controls and filters described in FIG. 6 is an overtone selector circuit, asindicated at 114 in-FIG. 6. This circuit provides the function of changing the overtone structure of the output as a function of breath intensity and for lip pressure. The overtone selector circuitincludes a set of analog multipliers 116 having as one input the output signals F 1 through F from each of the band pass filters 111 and control signals from an analog function fitter 115. The input control signal to the analog function fitter 1 is the weighted sum of the output signals, e,, from the air flow transducer, ande from the lip pressure transducer. The output signals from the analog multipliers 116 are provided to an adder 117 and the summed output signal from the adder is provided to mixing control 118. Also supplied to mixing control 118 is an output signal from adder 120. The output of mixing control 118 is applied to modulator 121. Elements 126,127 and 128 form the output silencing circuit. The circuit includes a differentiator 128 to which is applied the signal L(e,, De from the keying lag unit 101. The differentiated signal is applied to a weighting circuit designated absolute value circuit 127 and this weighted value is then subtracted in subtractor 126 from the signal e applied to the modulator 121.

In FIG. 7 there is illustrated a suitable filter design for each stage of the band pass filters 1 1 1. The signal input e, to the filters is coupled through the resistor 142 to the input terminal of an operational amplifier 150 having a feedback resistor 141. The output from the operational amplifier 150 is also connected to multiplier131, the second signal to multiplier 131 being from control input terminal 130. Input terminal 130 receives its signal from lagcircuit 110 and this signal may be expressed as L[e,,+(e,,+De,)]. The output from multiplier 131 is connected through resistor 132 and capacitor 133 to another multiplier 135. An operational amplifier 146 is connected across capacitor 133. The second input to multiplier 135 is provided directly from the control input terminal 130. The output from multiplier 135 is coupled through a second resistor 134 and capacitor 136 in series to the input resistor 140 of operational amplifier 150. Another operational amplifier 148 is connected across capacitor 136 and the output ter minal of operational amplifier 150 is connected through potentiometer 152 to the output terminal of operational amplifier 148. The arm of potentiometer 152 is'connected through capacitor 151 to the input terminal of operational amplifier 146. The output of operational amplifier 146 is connected to ground through potentiometer 158 and to negative voltage.

supply V through series resistors 154 and 155 the junction between these two resistors being connected through the series combination of resistor 156 and diode 157 back to the input terminal of operational amplifier 146. The overall filter output signal is taken from the arm of potentiometer 158. Suitable values for each of the components havebeen set forth below.

TABLE I R132 10 KO. C133 0.02 .F R134 10 K0 C136 0.02 ).:.F R l0 K9 R141 l0 Kn R142 [0 KO C151 0.001 [.LF Potentiometer 152 I00 KO. Potentiometer 158 20 KO R154 10 KO R156 l0 Kn R 20 K!) The center frequency, f of the bandpass filter can be expressed as R the resistance value of resistors 132 and 134 C the capacitance value of capacitors 133 and 136 and A the-attenuation factor through the multipliers 131 or 135.

Since the signal applied to the control input terminal 130 affects the attenuation through the multipliers 131 and 135, then this control input signal affects the center frequency f of the bandpass filters. A typical response characteristic for the bandpass filter is shown in FIG. 7a. In the filter, potentiometer 152 provides an adjustment for the Q of the circuit. The diode 157 is a limiting element to provide a sine wave output when the filter is adjusted to be in the oscillatory mode.

1 1 FIG. 8 illustrates one configuration of an overtone selector circuit suitable for use in the circuitry of FIG.

.6. The bandpass filter signals F F F F and F, are

supplied as one input to a series of multipliers 116a through 1 16c. A second input to each of these multipliers is supplied from the function fitter elements 115a through 115e. The input signal to the function fitter elements 115a through 1l5e is supplied from the adder which weights and sums the transducer outputs e and e,. The function fitter elements are circuit elements which provide in response to a varying input DC signal, an output DC signal which varies in accordance with a predetermined function. Thus if, for example, the input signal (Ke Ke,) were to increase linearly through a set of values, the function filter element 115a might be arrange'dto provide for an initial increase of output signal, then, at andabove a particular input DC level, for

a decrease in output signal. Each of the function fitters may be arranged to provide a particular response suitable for the particular overtone characteristics desired.

Additional adjustments are provided bythe series of weighting potentiometers 160, 161', 162, 163 and 164 coupled to theoutputs of the series of multipliers. The outputs from the adjustable potentiometers 160 through 164 are summed in adder 117, which is shown as an operational amplifier 170 with a feedback potentiometer 171 controlling the-overall gain. The output from the adder 117 is connected to one end of mixing control 118, the other end being connected to the output of adder- 120; The arm of 118 is connected to the multiplier 121. This mixing control allows a proportioning of the contribution from'the main filter output and. the overtone-selector output. The potentiometers 160 through l64"allow weighting adjustments controllin g'the proportion from each filter which will be applied to the adder 117. In FIG. 9 there are illustrated typical output functions for the-overtone selector circuit illustrated in FIG. 8, as the signal (Ke ke,,) from the input adder changes the contributions from each filter to the overall output harmonic structure changes. Thus, for example, filter output F1 is seen to commence at a very low value of (Ke Ke,,) and to peak and-then decrease to substantially zero level at about the same value of (Ke Ke,,) at which filter F4 commences to provide an output. The shape of these output responses is controlled by the function fitter elements which control the outputs from the band pass filters via their respective multipliers. While a particular configuration is shown in FIG. 9, as a suitable example, it will be understood that this overall circuit provides for complete control flexibility in terms of changing overtones of the basic instrument output in proportion to breath intensity and/or lip pressure. In the circuit shown, the band pass filters 111 provide the discrete harmonic signals :for the overtone circuit. Alternatively a completely separate set of filters might be employed to provide these input signals for the overtone circuit with the input signals now applied to band pass filters 111 being provided to those filters. FIG. 10 is an illustration in block diagrammatic form of the keying and interpose circuits which produce the varying DC output voltage e,,. The circuit includes a series of switches 21 through 31, which correspond to the keys illustrated in FIGS. 1 and 2 and also as shown on the fingering charts in FIGS. 11, 12 and 13. While the switches are shown as mechanical switches, utilizing soft conductive plastic for proper feel it will be understood that the actuating portion would typically be in the fingering keys and that transistor switches would be employed in the actual detailed circuitry. These actuating portions could be actual physical keys which close electrical contacts upon being actuated, or might be simply concentric electrodes with a high impedance gap, the players finger then providing a low impedance path between the electrodes to close the switch. A series of individual resistors 162 through 168 are arranged to form an overall resistance R, which in series with resistance R, shown as resistor 16], constitutes the input resistor to operational amplifier 185. Each of the switches 21, 24, 25, 26, 29, 30 and 31 are normally closed. Thus when the keys are all depressed, opening each of these switches, resistances R, and R are in series and the current from the reference voltage into the input terminal of amplifier 185 is E /R,,+R,,. Under these conditions R ='R Each of the resistances 162 through 168 are designed to providea current change in the same proportion as the frequency changes in a whole tone musical scale. Therefore, as each of the keys are raised, commencing with key 21', the current into theinput terminal of amplifier 185 increases through an octave of whole tempered tones (C-D-E-F-G-A-B-C).

Operational amplifier 185 is provided with a feed back resistor 169 and two other feedback resistors 170 and 171 which may be switched into the circuit by operation of the octave keys 32 and 33.Resistor 169 and resistor 170 each have twice the resistance value'of resistor 171. Accordingly, when both octave keys 32 and 33 are released, resistors 169, 170 and 171 are all in parallel. When key 32 is depressed,'only resistors 169 and 170 remain in parallel as the feedback resistors and accordingly the output signal from amplifier 185 is doubled. When both octave keys 32 and 33 are de pressed, however, onlyresistor 169 remains in the feedback loop thereby providing a' factor of four increase in the output signals from amplifier 185. As a result, the output signal from amplifier 185 may be varied over a range of four octaves, one octave in whole tone steps, by operation of the keys 21 through 31 and three additional octave steps.

The input signal to the second operational amplifier 186 is the output signal, e,', from amplifier 185 divided by a resistance value determinedvby the selection of the keys. Thus when keys 22, 23, 27 and 28 are released and no cross fingering is employed, then this resistance value equals the sum of the reciprocals of the resistances of resistors 172, 173, 174 and 178. Feedback resistors 179 and 180 around amplifier 186 are selected 7 to control the value of the output signals 2;, to be a suitable one for application to oscillator 102. The resistance 180 is a potentiometer, allowing adjustment of its resistance value to provide a change in the musical tuning or key of the instrument. As mentioned earlier, the selection of keys operates electronic switching circuits and accordingly in this instrument flexibilities in fingering arrangements are possible that cannot be achieved in an acoustical instrument.

One particular advantage of this arrangement is that the fingering from octave to octave may be uniform. Other advantages include the possibility of double sharps and double flats and also the fingering for interposed chromatics can be arbitrarily arranged to be most physically convenient for the performer.

in the input circuit to amplifier 186, resistors 173 through 178 are used to add or subtract the input current in semi-tone amounts (approximately 6 percent) according to whether they are included in the circuit (sharp) or removed from the circuit (fiat). Keys 22 and 27 are normally closed and depressing either one of these keys removes a semi-tone resistor, thereby reducing the output voltage e by approximately 6 percent. Depressing both keys reduces e by approximately 12 percent (double flat). In similarfashion depressing either one of the keys 23 or 28 adds one of the semitone tone resistors 176 or 177, while depressing both keys simultaneously produces a double sharp.

.The circuit includes a number of logic elements for providing certain interposes, normally used in the Boehm system of woodwind fingering. These interposes are logic elements 190, 191, 192 and 193 and provide that players familiar with the woodwind instruments may employ these interposes. The logic elements may be formed from typical logic gating. For example, logic element 190 (F sharp or G fiat) is actuated when keys 25, 29, 30 and 31 are depressed. This provides an output signal which opens switch 35 dropping resistor 178 out of the input circuit to amplifier 186. Similarly logic element 191 (A flat) is actuated when key 26. is closed in conjunction with keys 30 and 31 and provides the same output action as logic element 190. Logic element 193 (B flat) provides its output signal to actuate the same switch 35 in response to keys 26 and 31 being depressed. Similarly C sharp is played whenever all keys are open, and C natural is played when key 30 is depressed. Because of the arrangement which permits the use of double sharps and double flats, the instrument may be made to cover a full tone lower and a full tone higher than can be covered with the corresponding acoustic fingering system. This allows fingering interposes to be used in playing certain passages without changing octaves.

'FIGS. 11, 12 and 13 are fingering charts for use in the modified Boehm system of this keying logic to produce the specific notes indicated.

While the invention has been described in terms of specific circuitry and logic components, it will be appreciated that there are a number of variations in the circuitry possible, such as a keyboard or other input device to couple" the instrument to the player. The instrument may, as above indicated, be employed to produce tones substantially identical to that of a clarinet or other conventional wind instrument by selection of the keys and weighting factors; Entirelydifferent arrangements, not presently found in any of the classic wind instruments may, of course, be achieved by appropriate weighting of the various adjustments within the circuit and by changing the weighting factors associated with the transducer output signals. Also, while theinstrument has been described in terms of a performance with theperformer using it to produce a substantially instantaneous musical output, it will be understood that the instrument might be employed to produce not only the instantaneous musical output, but also the electrical control signals e,,,, e and e may be recorded on a storage medium and substantially applied tothe tone generating circuitry to reproduce this musical output without the performer. Another technique mightinvolve recording the electrical driving signals for the acoustic output on a storage medium and subsequently employing these with the acoustic output device, such as a loudspeaker to reproduce the music.

We claim:

1 A musical instrument to be played by a performer comprising,

an audio output means,

a signal generator producing an output signal including a fundamental frequency and one or more harmonics of that frequency, said signal generator including,

an oscillator for producing output signals at a controlled frequency and a coupling means for coupling these signal generator output signals from said signal generator to said audio output means,

' first and second control means operable by said performer to produce first and second continuously variable control signals, one of said signals being applied to said signal generator to control independently of frequency the harmonic content of the signals from said signal generator and a different one of said signals being applied to said signal generator to control the amplitude of the signals from said signal generator.

2. A musical instrument as in claim 1 and further including a keying means producing discontinuous outmounted on said mouthpiece, said transducer providing output signals which vary in response to changes in .the performers embouchure.

5. A musical instrument in accordance with claim 3 wherein said second control means comprises a transducer mounted on said mouthpiece, said transducer providing output signals which vary in accordance with changes in the performers lip pressure.

6. A musical instrument in accordance with claim 2 wherein said musical instrument includes a mouthpiece and said first control means comprises an air flow transducer mounted in said mouthpiece and said second control means comprises a second transducer mounted on said mouthpiece, said second transducer providing output signals which vary in response to changes in the performers lip pressure.

7. A musical instrument in accordance with claim 5 wherein said mouthpiece includes a reed and said second transducer is mounted on said reed to provide output signals varying with variations in position of said reed.

8. A musical instrument in accordance with claim 1 wherein said coupling means includes a comparator, adder combination and a manually adjustable reference voltage, said comparator adder combination being coupled to the output from said oscillator and receiving signals from said manually adjustable reference voltage and from at least one of said first and second control means, the output from said comparator being provided as the output from said signal generator.

9. A musical instrument in accordance with claim 3 further including a silencing circuit including a signal subtracting element interposed between said air flow transducer and said audio output means, means for providing a subtracting input signal to said subtractor, said subtracting signal varying with variations in the signal from said keying means to said oscillator, thereby subtracting from said air flow transducer signal a signal which varies in accordance with changes in said keying signal.

10. Circuitry in accordance with claim 9 and further including a series of bandpass filters having variable center frequencies controlled by applied voltages, said filters being arranged such that the center frequencies vary in accordance with variations in said oscillator repetition frequencies.

11. A musical instrument in accordance with claim 2 wherein said keying means comprises a plurality of keys generally arranged in physical disposition in accordance with a Boehm fingering arrangement and providing output frequencies producing musical notes generally in accordance with a Boehm fingering arrangement, but further including first and second flat keys and first and second sharp keys, the contribution from each of said flat and sharp keys being cumulative with the contributions from the other of said sharp and flat keys, whereby actuating both of said sharp keys orboth of said flat keys changes the note designated by the fingering on the remainder of said keys by a full tone.

12. A musical instrument to be played by a performer comprising,

an audio output means,

a signal generator producing an output signal of generally triangular waveform including a fundamental frequency and one or more harmonics of that frequency, said signal generator including,

an oscillator producing a generally triangular output waveform at a controlled repetition frequency, and

a coupling means for coupling the output signal from said signal generator to said audio output means,

a first transducer operable by said performer to produce a first continuously variable control signal and a second transducer operable by said performer to produce a second continuously variable control signal, the output from said first transducer being applied to said signal generator to change the shape of the waveform from said oscillator independently of changes in frequency and the output from said second transducer being applied to said signal generator to change the amplitude of the output signal from said oscillator.

13. A musical instrument in accordance with claim 12 and further including a keying means operable by the performer and producing output signals coupled to said oscillator to control the repetition frequency produced by said oscillator.

14. A musical instrument in accordance with claim 12 wherein said signal generator includes a comparator coupled to the output signal from said oscillator and a manually adjustable reference voltage connected to said comparator, and wherein said first transducer output signal is applied to said comparator, said comparator providing a two-level output signal, the duration of the signal at either level being controlled by the signals applied to said comparator.

15. A musical instrument in accordance with claim 14 wherein the two-level output signal from said comparator is applied to a lag circuit providing a generally triangular output waveform, the ratio of rise time to fall 7 time of said triangular waveform being controlled by the comparative time duration of the output signal from said comparator or at its first and second levels.

16 A musical instrument to be played by a performer comprising,

an audio output means,

an oscillator producing output signals at a controlled repetition frequency and having a waveform which includes the fundamental repetition frequency and one or more harmonics of that frequency,

oscillator control means operable by said performer for varying the frequency of said oscillator within a predetermined range,

a plurality of bandpass filters, with the center frequencies of each of said filters relative to the others remaining in fixed relation,

filter control means operable by said performer for varying the center frequencies of all of said filters to track with variations in the frequency of said oscillator, the output of said oscillator being connected to the input to said bandpass filters and the output from said bandpass filters being coupled to said audio output means.

17. A musical instrument in accordance with claim 16 wherein said oscillator control means comprises,

a mouthpiece transducer generating control signals varying in response to variations in the performers embouchure,

keying means producing output signals in response to the performers keying action, and

combining means for combining said mouthpiece transducer signal and said keying means output signal to generate the oscillator control signal.

18. A musical instrument in accordance with claim 17 wherein said mouthpiece transducer signal is added to said keying signal in weighted proportion for controlling the repetition frequency of said oscillator.

19. A musical instrument in accordance with claim 17 wherein said filter control means includes a time delay circuit positioned between said filter control means and said filters for varying the time response characteristic of said control means.

20. A musical instrument in accordance with claim 16 and further including a mouthpiece having an air flow transducer responsive to variation in performers breath blown into said mouthpiece to produce output signals and wherein said musical instrument further includes a modulating element, the'output signals from said bandpass filters being applied as one input to said modulating element and the output signal from said air flow transducer being applied as a second input to said modulator, thereby providing an output signal to said audio output means having an amplitude varying in accordance with variations in the amplitude of the output signal from said first transducer.

21. A musical instrument in accordance with claim 17 and further including a mouthpiece having an air flow transducer responsive to variation in performers breath blown into said mouthpiece to produce output signals and wherein said musical instrument further includes a modulating element, the output signals from said bandpass filters being applied as one input to said modulating element and the output signal from said air flow transducer being applied as a second input to said modulator, thereby providing an output signal to said audio output means having an amplitude varying in accordance with variations in the amplitude of the output signal from said first transducer.

22. A musical instrument in accordance with claim 21 and further including an overtone circuit for generating, in response to signals from either said air flow transducer or said embouchure transducer, a series of overtone components according to a predetermined function and combining means for combining said overtone components with the output signals from said filters.

23. A musical instrument in accordance with claim 22 wherein said overtone circuit comprises a plurality of function fitter elements and a corresponding plurality of multipliers, each function fitter providing its output signal as one input to a corresponding one of said multipliers, second inputs to each of said multipliers being supplied from corresponding ones of said bandpass filters, and means for supplying as input voltage signals to said function fitter a signal which is a combination of the output signal from said air flow transducer and said embouchure transducer.

24. Circuitry for use in a musical instrument to be played by a performer, said instrument including audio output means and providing control signals in the form of at least two continuously variable DC voltages, which are varied in response to actions of said performer, comprising,

an oscillator producing output signals at a repetition frequency controlled by one of said control signals,

a comparator coupled to said oscillator and providing output signals to said audio output means having a repetition frequency controlled by said oscillator and a wave shape controlled by another of said control signals. 

1. A musical instrument to be played by a performer comprising, an audio output means, a signal generator producing an output signal including a fundamental frequency and one or more harmonics of that frequency, said signal generator including, an oscillator for producing output signals at a controlled frequency and a coupling means for coupling these signal generator output signals from said signal generator to said audio output means, first and second control means operable by said performer to produce first and second continuously variable control signals, one of said signals being applied to said signal generator to control independently of frequency the harmonic content of the signals from said signal generator and a different one of said signals being applied to said signal generator to control the amplitude of the signals from said signal generator.
 2. A musical instrument as in claim 1 and further including a keying means producing discontinuous output signals in response to the performer''s keying action, said keying means output signals being applied to said oscillator to control the frequency of said oscillator.
 3. A musical instrument in accordance with claim 1 wherein said musical instrument includes a mouthpiece and said first control means comprises an air flow transducer mounted in a mouthpiece.
 4. A musical instrument in accordance with claim 1 wherein said musical instrument includes a mouthpiece and said second control means comprises a transducer mounted on said mouthpiece, said transducer providing output signals which vary in response to changes in the performer''s embouchure.
 5. A musical instrument in accordance with claim 3 wherein said second control means comprises a transducer mounted on said mouthpiece, said transducer providing output signals which vary in accordance with changes in the performer''s lip pressure.
 6. A musical instrument in accordance with claim 2 wherein said musical instrument includes a mouthpiece and said first control means comprises an air flow transducer mounted in said mouthpiece and said second control means comprises a second transducer mounted on said mouthpiece, said second transducer providing output signals which vary in response to changes in the performer''s lip pressure.
 7. A musical instrument in accordance with claim 5 wherein said mouthpiece includes a reed and said second transducer is mounted on said reed to provide output signals varying with variations in position of said reed.
 8. A musical instrument in accordance with claim 1 wherein said coupling means includes a comparator, adder combination and a manually adjustable reference voltage, said comparator adder combination being coupled to the output from said oscillator and receiving signals from said manually adjustable reference voltage and from at least one of said first and second control means, the output from said comparator being provided as the output from said signal generator.
 9. A musical instrument in accordance with claim 3 further including a silencing circuit including a signal subtracting element interposed between said air flow transducer and said audio output means, means for providing a subtracting input signal to said subtractor, said subtracting signal varying with variations in the signal from said keying means to said oscillator, thereby subtracting from said air flow transducer signal a signal which varies in accordance with changes in said keying signal.
 10. Circuitry in accordance with claim 9 and further including a series of bandpass filters having variable center frequencies controlled by applied voltages, said filters being arranged such that the center frequencies vary in accordance with variations in said oscillator repetition frequencies.
 11. A musical instrument in accordance with claim 2 wherein said keying means comprises a plurality of keys generally arranged in physical disposition in accordance with a Boehm fingering arrangement and providing output frequencies producing musical notes generally in accordance with a Boehm fingering arrangement, but further including first and second flat keys and first and second sharp keys, the contribution from each of said flat and sharp keys being cumulative with the contributions from the other of said sharp and flat keys, whereby actuating both of said sharp keys or both of said flat keys changes the note designated by the fingering on the remainder of said keys by a full tone.
 12. A musical instrument to be played by a performer comprising, an audio output means, a signal generator producing an output signal of generally triangular waveform including a fundamental frequency and one or more harmonics of that frequency, said signal generator including, an oscillator producing a generally triangular output waveform at a controlled repetition frequency, and a coupling means for coupling the output signal from said signal generator to said audio output means, a first transducer operable by said performer to produce a first continuously variable control signal and a second transducer operable by said performer to produce a second continuously variable control signal, the output from said first transducer being applied to said signal generator to change the shape of the waveform from said oscillator independently of changes in frequency and the output from said second transducer being applied to said signal generator to change the amplitude of the output signal from said oscillator.
 13. A musical instrument in accordance with claim 12 and further including a keying means operable by the performer and producing output signals coupled to said oscillator to control the repetition frequency produced by said oscillator.
 14. A musical instrument in accordance with claim 12 wherein said signal generator includes a comparator coupled to the output signal from said oscillator and a manually adjustable reference voltage connected to said comparator, and wherein said first transducer output signal is applied to said comparator, said comparator providing a two-level output signal, the duration of the signal at either level being controlled by the signals applied to said comparator.
 15. A musical instrument in accordance with claim 14 wherein the two-level output signal from said comparator is applied to a lag circuit providing a generally triangular output waveform, the ratio of rise time to fall time of said triangular waveform being controlled by the comparative time duration of the output signal from said comparator or at its first and second levels.
 16. A musical instrument to be played by a performer comprising, an audio output means, an oscillator producing output signals at a controlled repetition frequency and having a waveform which includes the fundamental repetition frequency and one or more harmonics of that frequency, oscillator control means operable by said performer for varying the frequency of said oscillator within a predetermined range, a plurality of bandpass filters, with the center frequencies of each of said filters relative to the others remaining in fixed relation, filter control means operable by said performer for varying the center frequencies of all of said filters to track with variations in the frequency of said oscillator, the output of said oscillator being connected to the input to said bandpass filters and the output from said bandpass filters being coupled to said audio output means.
 17. A musical instrument in accordance with claim 16 wherein said oscillator control means comprises, a mouthpiece transducer generating control signals varying in response to variations in the performer''s embouchure, keying means producing output signals in response to the performers keying action, and combining means for combinIng said mouthpiece transducer signal and said keying means output signal to generate the oscillator control signal.
 18. A musical instrument in accordance with claim 17 wherein said mouthpiece transducer signal is added to said keying signal in weighted proportion for controlling the repetition frequency of said oscillator.
 19. A musical instrument in accordance with claim 17 wherein said filter control means includes a time delay circuit positioned between said filter control means and said filters for varying the time response characteristic of said control means.
 20. A musical instrument in accordance with claim 16 and further including a mouthpiece having an air flow transducer responsive to variation in performer''s breath blown into said mouthpiece to produce output signals and wherein said musical instrument further includes a modulating element, the output signals from said bandpass filters being applied as one input to said modulating element and the output signal from said air flow transducer being applied as a second input to said modulator, thereby providing an output signal to said audio output means having an amplitude varying in accordance with variations in the amplitude of the output signal from said first transducer.
 21. A musical instrument in accordance with claim 17 and further including a mouthpiece having an air flow transducer responsive to variation in performer''s breath blown into said mouthpiece to produce output signals and wherein said musical instrument further includes a modulating element, the output signals from said bandpass filters being applied as one input to said modulating element and the output signal from said air flow transducer being applied as a second input to said modulator, thereby providing an output signal to said audio output means having an amplitude varying in accordance with variations in the amplitude of the output signal from said first transducer.
 22. A musical instrument in accordance with claim 21 and further including an overtone circuit for generating, in response to signals from either said air flow transducer or said embouchure transducer, a series of overtone components according to a predetermined function and combining means for combining said overtone components with the output signals from said filters.
 23. A musical instrument in accordance with claim 22 wherein said overtone circuit comprises a plurality of function fitter elements and a corresponding plurality of multipliers, each function fitter providing its output signal as one input to a corresponding one of said multipliers, second inputs to each of said multipliers being supplied from corresponding ones of said bandpass filters, and means for supplying as input voltage signals to said function fitter a signal which is a combination of the output signal from said air flow transducer and said embouchure transducer.
 24. Circuitry for use in a musical instrument to be played by a performer, said instrument including audio output means and providing control signals in the form of at least two continuously variable DC voltages, which are varied in response to actions of said performer, comprising, an oscillator producing output signals at a repetition frequency controlled by one of said control signals, a comparator coupled to said oscillator and providing output signals to said audio output means having a repetition frequency controlled by said oscillator and a wave shape controlled by another of said control signals. 